<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<div>
		<select name="wife" id="">
		<option value="皇后">皇后</option>
		<option value="皇贵妃">皇贵妃</option>
		<option value="贵妃">贵妃</option>
		<option value="德妃">德妃</option>
		<option value="淑妃">淑妃</option>
		<option value="令妃">令妃</option>
		<option value="熹妃">熹妃</option>
		</select>
		<input type="button" value="翻牌">
	</div>

	
</body>
<script>
		var btn = document.querySelector("input");
		var opt = document.querySelectorAll("option");

		btn.onclick = function(){

			var num = parseInt(Math.random()*7);

			opt[num].selected = true;
		}
</script>
</html>